Local area networks (LANs) often use unshielded twisted pair (UTP) cables as transmission lines for high frequency communication of data between devices. The UTP cable often has four twisted pairs, each pair including two conductors or wires. Some LAN cabling schemes only use four of these wires, leaving four wires unused.
Current may be created in the unused wires due to differences in the ground potential between the LAN devices, coupling of currents from adjacent used wires, or an impedance mismatch between the wires and the local ground. If the unused wires are not properly terminated in the LAN device, the unused wires may produce unwanted electrical noise, radiated electromagnetic emissions, and electrostatic discharge (ESD) and electrical fast transient (EFT) events on or near the UTP cable.